1. Field of the Invention
The present invention relates to an image forming apparatus, for example, an electrophotography type, an electrostatic recording type image forming apparatus, or the like, and more particularly, to a color image forming apparatus such as a color copying machine, a color printer, or the similar apparatus, wherein a plurality of image forming members are provided to form a plurality of images, each different in color, on respective image storing members, and then these images are transferred, one on another, in turn, on the same recording sheet held and transported by a recording sheet transporting member.
2. Description of the Related Art
In an image forming apparatus which includes an endless image-transfer belt having a seam and which transfers an image to a recording sheet held on the image-transfer belt from a photosensitive drum, if image transferring is performed when the recording sheet is located on the seam, a portion of the image may not be transferred on the recording sheet, resulting in a poor image.
In order to solve the problem, an image forming apparatus has been proposed by, for example, Japanese Unexamined Laid-open Patent Publication No. H6(1994)-35262. The image forming apparatus is provided with a seam detector for detecting the seam and an image detector for detecting the image status. In the image forming apparatus, when no image, or when character images, line images, or single-color images are to be transferred to the recording sheet, it is assumed that the seam does not cause a poor image transfer. Therefore, the recording sheet is fed regardless of the seam. In other cases, the recording sheet is fed so as not to be located on the seam.
However, in the above-mentioned conventional image forming apparatus, though poor image transferring seldom occurs when the image only consists of characters, lines or a single-color, a poor image transferring still may occur when a portion of a character is located on the seam, especially when the character is very small.
On the other hand, when transferring a color image including a character and a picture, when the size of the image is smaller than that of the recording sheet, or when the image has, at its center portion, a blank area(so called "center erase of 2 in 1"), if the blank area portion is located on the seam, no problem will occur when transferring an image. Nevertheless, the recording sheet will be fed such that the recording sheet is not positioned on the seam even though image consists of characters, lines or a single-color. This causes decreased efficiency for feeding the recording sheet, resulting in decreased productivity for the whole apparatus.